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Discussion Starter #1
Hi thee,

I posted this in a similar forum - I'm due to pick up my Prius around mid-April here in PA. I'm a little concerned by some of the posters who say they've had problems with the traction control - the car 'dying when going up a slight incline that's a little slippery.
All cars I know have had a button to disable tracation control in these situations, so you can at least 'continue' and try and pull yourself out of a stop.
Is there ANY solution to this problem? I know some have stated to get snow tires, or better tires. I suppose I could, but I haven't bought snows since I had a '75 Fiesta. Cars should come with all weather tires. I guess I'm having some doubts and this may actually kill the deal for me, since I place a pretty high importance on not getting stuck. : -(
Anyone?
Thank you.
Kevin
 

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There is no traction control defeat on the Prius because the traction control is there also to protect the MGs from overreving and damage. This is a necessity of the system.

The Goodyear Integritys are not all that wonderful. Decent on dry pavement, ok on wet. I haven't found slush to be a problem, but might not be that good in really adverse situations. The biggest weakness with traction isn't the vehicle, it is the rubber it is riding on. There is advice out there that you can trade up your tires for better ones from Goodyear so long as you have less than 500 miles on them. With that said, if your dealer won't move you up as part of your sale, then hightail it to your nearest Goodyear shop and ask about trading them up for Comfortreds or another tire that is a better all around performer. You will have to pay them something to do this, but it won't be as much as for a whole set of tires.

I have not had a bad traction experience yet with the Prius, in spite of the less than wonderful rubber they have been sent out of the factory with. We had a very mild winter up here so my experience is not very solid, however the snow and slush we did have was not a problem at all. That means we didn't have much.

This should not be a deal breaker for you. In fact, I think that many of the claims of loss of traction have been by drivers that are placing their vehicles in extreme conditions. If I were to drive my older vehicle that doesn't have traction control, spinning my way out of a stuck or nearly stuck situation is less than ideal. It puts a lot of wear on bearings, transmissions, gears and other transaxle parts that normal driving does not.
 

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Discussion Starter #3
Thanks for the reply. I guess I was getting nervous after reading some of these postings.
Just wish Toyota thought to force the Prius into using the gas engine rather than the elec motor when disabling the Traction Control. I guess I'll check out tire suggestions...
Thanks,
Kevin
 

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Once you learn more about how the system is put together, you'll realize that the electric motor is far smoother and easier to control than a gasoline engine ever could be, especially the Prius gasoline engine which purposely has a very slow response to avoid pollution causing conditions. Not only that, but the electric motor can provide both far more and far less torque to the wheels than the gasoline engine can. So if there were a traction control defeat switch, it should not force the gasoline engine to start, rather it should allow the electric motor to go about its business despite any wheel slipping that occurs. Posi-traction would help a lot also.

But a better all around choice for these conditions is a good implementation of all-wheel drive. Rather than looking for a front wheel drive car with traction control defeat so that you can trash it, perhaps you should look into a Subaru or Audi all-wheel drive sedan.

Even with traction control defeat, if you find yourself spinning and burning your way out of a snow trap more than twice in the lifetime of the car, you bought the wrong car. Seriously.
 

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"the Prius gasoline engine which purposely has a very slow response"

Yes, this is a beef I have; at certain speeds, stomping the pedal yields a 2 second delay before meaningful acceleration occurs. In some traffic situations, it's a real drag!
 

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It appears as if there is a delay, but if you look at your speedo right after that delay, you are already clocking 7MPH.
 

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KTPhil said:
"the Prius gasoline engine which purposely has a very slow response"

Yes, this is a beef I have; at certain speeds, stomping the pedal yields a 2 second delay before meaningful acceleration occurs. In some traffic situations, it's a real drag!
By certain speeds, I take it you mean above 50 MPH or so. All's I can say is bummer, if you really wanted a muscle car I guess you should have bought one instead of a low emission car. And you'll also have to avoid cheats like turbo chargers because they have a lag also. Just go buy yourself a huge engine and waste it 99% of your drive time. Then feel bad when you realize just how much they had to crush its spirit to get it to meet current emission standards.

No, the Prius is not a muscle car and was never intended to be one. But I hear rumors that the Hybrid Hylander is trying to sneak into that category.
 

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The behavior at reverse driving and traction control can be bad:

I drove forwards on a slippery bled off grassland. I tried to return backwards to the road (only the electrical engine is used) but it failed. I turned around and forward there was no problem to return to the road. Mabye the electrical engine is not powerful enough or the traction conrol does not work fine in reverse mode.

Robert
 

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kevin54 said:
Hi thee,

I posted this in a similar forum - I'm due to pick up my Prius around mid-April here in PA. I'm a little concerned by some of the posters who say they've had problems with the traction control - the car 'dying when going up a slight incline that's a little slippery.
All cars I know have had a button to disable tracation control in these situations, so you can at least 'continue' and try and pull yourself out of a stop.
Is there ANY solution to this problem? I know some have stated to get snow tires, or better tires. I suppose I could, but I haven't bought snows since I had a '75 Fiesta. Cars should come with all weather tires. I guess I'm having some doubts and this may actually kill the deal for me, since I place a pretty high importance on not getting stuck. : -(
Anyone?
Thank you.
Kevin
I think we hat the same situation:

http://priusonline.com/viewtopic.php?t=4504
 

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"By certain speeds, I take it you mean above 50 MPH or so. All's I can say is bummer, if you really wanted a muscle car I guess you should have bought one instead of a low emission car. "

Nope, nothing of the sort.

It happens around 20-30mph. I stomp it to get going up an onramp, or to catch a closing hole in suburban traffic. Sometimes it's quick, other times there is a delay you can count to 3 before you are accelerating.

It hasn't happened often enough to really characterize it. I am guessing there is a lag to spin up an MG in order to re-ratio the PSD for acceleration. Mass still takes time to get up to speed (or slow down), and the ECU might delay the accel until the ratio is right. Perhaps on those occasions my driving fits a pattern that typocally calls for a tall gear ratio, and it isn't expecting the sudden call for acceleration, so it has to spin/brake a motor to be ready. Urban traffic calls for quick throttle response, and on those occasions I don't have it, really my only complaint about the drivability of the car.
 

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RSnyder said:
And you'll also have to avoid cheats like turbo chargers because they have a lag also.
Just an FYI, I've driven an '84 Saab turbo, and a '01 Jetta turbo... Turbo lag may have been a factor 20 years ago, but it isn't anymore.
 

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I'd really like it if I see less traction control action after I get the TripleTreds next week. Sale supposedly starts 5/19; s/b $71 each after rebate, plus the extra stuff they add to tire prices.

ANY time I accelerate from a stopped position and have the wheels cranked to either side, I feel the lack of power. Going straight, sometimes even on dry roads it kicks in. Darn often on wet ones. If there's less slip maybe there'll be less annoyance...
 

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Traction Control Problem

Motor Traction Control:

"If the wheels slip while the vehicle is being driven on a slippery road surface, MG2 (which is coupled directly to the wheels) will spin excessively, causing the relative rotational speed of the planetary gear unit to increase. This condition could damage the areas that suport the parts in the planetary gear unit, such as through seizure. In some cases, this condition could cause MG1 to generate an excesive amount of electricity. For this reason, if the HV ECU determines that MG2 is spinning excessively upon monitoring a sudden change in rotational speeds by way of the speed sensor signals, the HV ECU applies a brake force to suppress the rotation, in order to protect the planetary gear unit.

Furthermore , if only one of the drive wheels spins excessively, the HV ECU will monitor the speed difference between the right and left wheel by way of the speed sensors of the respective wheels, and the HV ECU will transmit a command to the skid control ECU in order to apply a brake to the wheel that is spinning excessively.

These controls achieve the same effect as the TRAC of the brake control system. "
-2004 Toyota Prius New Car Features Book-
Pu. No. NCF255U
 

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KTPhil said:
I am guessing there is a lag to spin up an MG in order to re-ratio the PSD for acceleration. Mass still takes time to get up to speed (or slow down), and the ECU might delay the accel until the ratio is right. Perhaps on those occasions my driving fits a pattern that typocally calls for a tall gear ratio
Could you explain that? From diagrams I've seen it seems the Prius has no "gears" to shift in the traditional sense. It's planetary gear arrangement with should be able to deliver additional torque/RPM on demand without a delay AFAICT. No?
 

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If a spinning gear set in a planetary drive must speed up/slow down/reverse direction in order to change the effective ratio, then that inertial delay will cause a temporary lag in response. Also, until the ICE is spun and producing power, it will not be fed into the drive system by such gear speed adjustments. There may also be algorithms to prevent likely overspeeding that introduce delays until relative speeds are within specs for the ICE, MGs, and gearsets.

These two delays are what I believe results in the 1-2 second lag in accelaration from a zero throttle positin to a max accel demand, such as a freeway onramp following a tight corner, or an attempt to squirt in stop and go traffic into the next lane and gun it.

The "preload" step is to lightly press the gas so the ICE is alerady fired up and matched in speed, but not hard enough to accelerate yet. That way there is less inertial lag in the PSD, and no delay in igniting the ICE.
 

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Thanks for the response. Interesting to work this through…

KTPhil said:
If a spinning gear set in a planetary drive must speed up/slow down/reverse direction in order to change the effective ratio, then that inertial delay will cause a temporary lag in response.
According to literature I've read on the ICE, at freeway speed the ICE should already be up to speed, even if it’s not combusting, hence the ratio already set. It can be spun at low resistance and is done so exactly to allow it to start again instantly. That's assuming it's even "off" which it shouldn't be at highway speeds. The electric batteries can't run the car for far by themsleves, so it would make no sense to shut off the ICE completly on the freeway very often. Throttle it down perhaps and agment that with the electric motors.

Regardless, the electric motor should be capable of adding acceleration any time, truly instantly. So, power is always available, acceleration instant from the MG and additionally from the ICE a moment later.

I suspect it's actually a human sensory/psychological issue due to lack of engine noise, as the forst acceleration surge will be from the MG. A person might notice the additional speed in a Prius after attaining it, and might hear the ICE rev to full a second or so later, hence the perceptual lag.
 

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The lag I posted about is in the range of 20-30mph (as my post clearly stated), a speed at which a closed-throttle ICE is not spinning.

Moving mass is not instantaneous. The ratio is adjusted by chaning the speed of electric motors, whose drive mass is far from zero. This delay is not psychological!

Simple test: Accelerate to 30mph, then let off. Let the car slow to 20mph, then stomp on the pedal.

Did you read the posts in this thread?
 

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KTPhil said:
The lag I posted about is in the range of 20-30mph (as my post clearly stated), a speed at which a closed-throttle ICE is not spinning.
Thanks for pointing out (again) what speed you're referring to. Somebody else was referring to freeway speeds.

As I understand it, you're postulating that the in the 20-30mph range the ICE is not only off, but not even spinning, therefore the electrics are spinning at an entirely wrong ratio for any ICE power input. Furthermore, the electrics must be at capacity and unable to provide the power surge themselves, hence the supposed lag while everything spins to the right ratio.

Frankly, I don't think that's correct.

I havn't noticed a delay there for one thing. Secondly it would make no sense to spin down the ICE that I can see, unless it's a real drag and the electrics were expected to power the vehicle 100% for a prolonged period. According to literature it's not intended to run completly on electric for long, and can't, as the batteries drain rapidly. Also according to lit on the Prius the ICE is very low drag to spin, and is kept spinning to rapidly restart on the fly. That is a critical design feature of the ICE.

KTPhil said:
The ratio is adjusted by chaning the speed of electric motors, whose drive mass is far from zero.
The mass of the electric motors is not the issue. Even presuming the ICE is completly still (which I doubt) they can still spin up or down, extremly quickly much faster than any gas engine. Regardless, mechaniclally one can change rate to adjust the ratio, adding power to spin the ICE, while the other is delivering more power as well, simultaneously for a net increase in acceleration and spinning up the ICE.

KTPhil said:
This delay is not psychological!
I doubt that. The kind of aceleration a car in the Prius class can manage is not very strong to begin with. An ordinary person jumping from a standstill to a run is more instantaneous acceleration than most sports cars can deliver. A mid sized sedan delivers a small fraction if that at best. Take away the sound and the prominant gear shift lurch a second after flooring it, from a Corolla or a Passat and there isn't much there to feel.

DanMan32 said:
It appears as if there is a delay, but if you look at your speedo right after that delay, you are already clocking 7MPH.
I tend to agree with Dan, and he does seem to be the real Prius expert here.

KTPhil said:
Did you read the posts in this thread?
Yes, actually I did. And just reread them carefully as well. You're the only person claming this problem, and the only one endorsing your theory of it. You claim it's intermittent as well. Others have pointed out the electrics have plenty of torque available, and that it may be your imagination.
 

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I'm not the only one (there have been multiple threads on lag on this board and on PC, though you are perhaps too new here to know this), and it happens every day under the circumstances I describe.

In fact, the lag is noticable enough that tailgaters at this onramp nearly rear-end me, because they accelerate, assuming I will also; they close on me until the ICE kicks in and I accelerate. Are they imagining it also?

Dan's comments are from a standstill, not 20mph. I do not read 7mph while accelerating from 20mph. You don't read as carefully as you claim.

When coasting at 20mph, the ICE is off and there is no evidence it is spinning. Why would it be? There is no power demand, it is under the maximum EV-only speed, and the throttle is closed.

If you can find your way around the laws of physics and show me how moving mass can be instantaneous, please share. Have you found a way around Newton's Laws?
 

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KTPhil said:
When coasting at 20mph, the ICE is off and there is no evidence it is spinning. Why would it be?
So you say. Unfortunatly there doesn't seem to be any evidence to support that theory. The only mention Toyota makes of shutting off the engine is at complete stops.

Nor does anyone else seem to share your alledged problem. I think you're an internet troll, with a credibility of about zero.

As far as why the ICE would be on, charging the battery for one reason, as Toyota literature specifically mentions. Why it would be kept spinning, even if not combusting, is to allow immediate power from the ICE. Which btw Toyota specifically mentions as a design feature of the IC. It can open its valves and spin at very low resistance for the specific purpose of starting up again immediatly, as Toyota lit describes. Alternativly it can spin at high resistance by closing valves, and is used in that way for engine breaking, but that takes a manual switch into Braking mode.

People who enable stealth mode discover how incredibly short range pure electric power is by itself, which is why the electric needs to be frequently recharged, and why the ICE needs to frequently run. Unlike a traditional ICE however, it can run at optimal RPM because the electric supply most of the additional power needed for stop and go driving.

KTPhil said:
If you can find your way around the laws of physic ..Have you found a way around Newton's Laws?
Escalating your opinion of whether the Prisus ICE is on or off to a law of physics is extreme hyperboly, a real internet troll windbag sort of thing to claim.
 
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